Sudden cardiac death (“SCD”) can be generally defined as death within one hour of the onset of symptoms without a previously-known disease or a disease that was expected to be lethal. SCD can also occur without symptoms or warnings signs. SCD is often described with respect to an unwitnessed death with the victim having been known to be alive less than 24 hours earlier.
SCD can kill its victims within minutes and often occurs in outwardly healthy people who have no known heart disease. Although it may occur in outwardly healthy people, most victims do have heart disease or other health problems, often without being aware of it. SCD claims about 300,000 lives a year in the United States and presents a public health challenge in that often the only indication a patient is at risk appears when the patient succumbs, without warning, to a heart failure episode.
In many cases, SCD victims suffer from ventricular tachycardia that degenerates into ventricular fibrillation. Ventricular tachycardia is a type of cardiac arrhythmia that is a serious, often-times, fatal condition characterized by rapid, uncontrolled, and ineffective beating of the heart. Ventricular fibrillation is a chaotic ventricular heart rhythm which produces little or no net blood flow from the heart, such that there is little or no net blood flow to the brain and other organs. Ventricular fibrillation, if not terminated, results in death. Researchers continue their efforts to predict the onset and triggers for such ventricular tachyarrhythmias and SCD.